Cutting force prediction considering force-deflection coupling in five-axis milling with fillet-end cutter

With the increasing demand for higher quality and performance of equipment and assembly in aerospace, shipbuilding, medical and other fields, the machining accuracy of parts is facing higher requirements. It is particularly important to predict the cutting force accurately, which is the main physical quantity in the machining process and basis of process inspection and quality control. In this paper, the cutting force model in five-axis milling with fillet-end cutter is proposed, which reveals the law of force-deflection coupling. Firstly, the initial cutter deflection model induced by the ideal cutting force ignoring the effect of deflection is built based on analysis of the geometric characteristics of fillet-end cutter. Then the undeformed chip thickness model is educed considering the cutter posture and cutter deflection. Further, the iterative method is utilized to resolve the coupling relationship between cutter deflection and cutting force. Finally, the cutting force model under force-deflection coupling is established for achieving more accurate prediction. To verify the effectiveness of the proposed cutting force model, the milling experiment is carried out on a five-axis milling center. The measured cutting force values are utilized to inspect the accuracy of prediction models considering and not considering force-deflection coupling respectively. The results show that the proposed method could improve the prediction accuracy of cutting force, which show the effectiveness of taking force-deflection coupling law into consideration clearly. The influence of cutter posture on cutting force is analyzed using the proposed cutting force model. The cutting force decreases with the increasing of lead angle or tilt angle, and the influence of tilt angle is greater than that of lead angle under experimental conditions of five-axis milling using the set process parameters.

A Bending-Machining Hybrid Process for Angular Dimensional Accuracy Enhancement

Bending is a fundamental manufacturing process to form sheet metals into intended angular geometries. Although the process has been extensively studied, predicting its accuracy is still challenging due to the Springback phenomenon inherent to the process. This research intends to combine bending and machining processes to improve bent workpiece angular dimensional accuracy. A minimum enclosing CAD model is first obtained by determining optimum thickness from the bend part CAD model to accommodate the estimated Springback in order to guide the selection of blank workpiece dimension for this bending/machining strategy. Then the machining areas are determined and the cutting forces are predicted to estimate the deformation in the machining process. Toolpath is planned on the surface profile considering both the cutter deflection and the incurred workpiece deformation during machining. This project aims to produce a bending part with the desired dimensional accuracy through a hybrid manufacturing approach. More importantly, it also provides a technological foundation to prototype angled parts at a low cost by avoiding high expenses in making new die.

Estimation of Cutter Deflection Based on Study of Cutting Force and Static Flexibility

In the tool orientation planning for five-axis sculptured surface machining, the geometrical constraints are usually considered. Actually, the effect of nongeometrical constraints on tool orientation planning is also important. This paper studied one nongeometrical constraint which was cutting force induced static deflection under different tool orientations, and proposed a cutter deflection model based on that. In the study of the cutting force, the undeformed chip thickness in filleted end milling was modeled by geometrical analysis and coordinate transformation of points at the cutting edge. In study of static flexibility of multi-axis machine, static flexibility of the entire machining system was taken into consideration. The multi-axis machining system was divided into the transmission axes-handle (AH) end and the cutting tool end. The equivalent shank method was developed to calculate the static flexibility of the AH end. In this method, static flexibility anisotropy of the AH end was considered, and the equivalent lengths of the AH end were obtained from calibration experiments. In cutter deflection modeling, force manipulability ellipsoid (FME) was applied to analyze the static flexibility of the AH end in arbitrary directions. Based on the synthetic static flexibility and average cutting force, cutter deflections were derived and estimated through developing program realization. The predicted results were compared with the experimental data obtained by machining 300 M steel curved surface workpiece, and a good agreement was shown, which indicated the effectiveness of the cutter deflection model. Additional experiments of machining flat workpiece were performed, and the relationship of cutter deflections and tool orientations were revealed directly. This work could be further employed to optimize tool orientations for suppressing the surface errors due to cutter deflections and achieving higher machining accuracy.

Modeling and Simulation of Milling Forces for Ball-End Cutter with Considering Comprehensive Factors

In this paper, influence mechanism of variously physical factors for milling force in any feed direction is studied during the milling process. Firstly, the effects of spindle eccentricity, cutter deflection and cutter vibration for the instantaneously undeformed cutting thickness are analyzed, and the mathematical expressions of chip thickness is set up. Then,on this basis of cutting force and chip load, the milling force model of ball-end mill with considering integrated physical factors is established though the differential method, and a simulation system for prediction of milling forces during the milling process is developed. This milling force model is verified through simulation and analysis of milling forces.

Research on the Influence Factors for the Deflection of Micro-Ball-End Cutter in Micro-End-Milling Process

Machining parameters and spindle radial runout have great influence on the micro-ball-end cutter deflection in the micro-end-milling process. In this study, a 3D (three-dimensional) thermal-mechanical FEM (finite element method) model of micro-milling with non-rigid cutter is built to study how radial runout, cutting depth, feed and spindle speed influence the cutter deflection when feed has the same direction with the spindle radial runout. Cutter deflection under different groove lengths, cutting depths, feeds and spindle speeds is investigated, which shows that cutter deflection increases with spindle radial runout significantly. The largest deflections with runout of 2μm are 3.26μm, 3.26μm, 4.71μm and 4.52μm respectively under the adopted machining conditions, while the largest deflections without runout are 1.85μm, 1.85μm, 2.26μm and 3.79μm respectively. It is also shown that the runout effect increases with groove length, cutting depth, while it decreases with feed.